Best drill bit to remove broke cobalt bit?

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bighammer

bighammer

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:banghead: As luck would have it I now have a snapped off 9/64ths cobalt bit in one of the exhaust manifold bolts. It's below the surface, and I've gone thru several new 5/32 bits, but it is taking forever, not much progress. :banghead:

Is there another type of bit that is harder than cobalt that I can use?
 
Titanium is the next step up.
 
Use a Reverse cut drill bit in reverse in your drill and it'll back it out.
 
If you can get a torch to it heat it red hot and it should draw the temper out of the bit and make it drill able.

May have to pull the head off to do it
 
My first thought was that you're hosed.
Way to drill a cobalt bit? Not that I can figure.
Grinding it out is the only thing I can think of.
High speed with an abasive bit of some type.
I predict you are going to wind up putting a helicoil in the hole.
 
I used small diamond tip grinder bits from Harbor Freight in my Dremel several years ago. It took an evening and I used up several of them but I got it.
 
If you can find someone "who is skilled' with a cutting torch you can blow it out of there.

By that I do NOT mean a plasma cutter.
 
Put a nut over the hole the bit is in and build up a weld up off the bit and out of the hole and weld it to the nut then back it out with a wrench. Tig would be best but it can be done with a mig also. I have done this technique several times on bits, bolts, ez outs etc. Never once has it failed me.

You can do the same technique on the bolt that's broke off. The heat from welding will loosen it up and it too will come out. The whole process takes about 10 min. As soon as the weld is not cherry red, start going after it with your wrench. Do not let it cool all the way off.
 
Cobalt and titanium bits are just high speed steel bits with a coating of titanium or cobalt. They are just surface hardened with this material. Weld to it or grind it out with a Dremel tool and a carbide bit would be your best bet. You may be able to draw the temper out by heating it but due to the fact that the broken bit is so jagged, you may break your drill bit trying to drill it out. I've never used a carbide bit but I've heard they do work. tmm
 
toolmanmike said:
Cobalt and titanium bits are just high speed steel bits with a coating of titanium or cobalt. They are just surface hardened with this material. Weld to it or grind it out with a Dremel tool and a carbide bit would be your best bet. You may be able to draw the temper out by heating it but due to the fact that the broken bit is so jagged, you may break your drill bit trying to drill it out. I've never used a carbide bit but I've heard they do work. tmm
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I was thinking along the same lines. Anything following that broken bit will not stay on center. Instead it would very likely hang and break.
A 1/4 diameter carbide tipped masonry bit might work will the exhaust manifold in place to serve as a guide. It might be best to just pull the head. A machine shop can throw it on a Bridgeport under a carbide end mill. Good luck with it.
 
A mate of mine once snapped off a tap in a hole....I used a Masonary bit with the drill set to hammer....it worked.
 
High carbon tools like taps and drill bits will burn out before the cast iron (low carbon) will. Oxy-acyl torch with a skilled hand would get it out.
 
One thing you could try if you have access to a stick welder.

Take a screwdriver that will contact the outer edge of the bit, hook your ground lead to it and contact the outer edge of the bit.

Put a rod in the stinger and hold it firmly centered on the bit, have someone turn the welder on and off. Bend the rod 90*, think handle, and give it a pull.

I might come out that way.
 
anything you do is going to put debris in the port so I hope the valve below it is closed for starters , most common mistake is using to much speed , slow the drill down and your bits will stay sharp , if you have a decent hammer drill , put it on reverse with hammer and you should be able to back it out , I would drill a smaller hole a little way into the center to create a pocket first . I do a lot of commercial door hardware and the fasteners provided are always soft chinese crap , couple that with guys who are too stupid/lazy to block out the inside of the frame prior to pouring it with concrete and I have broken a lot of taps , drill bits and bolts in my day .
 
I use Carbide Hi Roc drills to remove broken taps and hi speed/cobalt bits from all sorts of castings... Just try to put a drill guide in place over the suspect broken bit... Preferred would be to have someone with a Bridgeport or similar machine doing it with a carbide end mill...

Edit Note: A straight flute carbide Hi Roc will work in a guide bushing way better then a carbide tipped masonary bit... Just saying... Good Luck!
 
You guys are all walking around the block to go next door is all I can say! Drill this drill that bridgeport, end mill……..hoggg wash. It only takes 10 minutes with my method and no $$. Lol
 
Wow, thanks for all these suggestions. With all that I've read above, I'm going to try to implement some of the suggestions here... But... I'm not too confident with my mig welding capability, so it will attempt first with a masonry bit, with a carbide tip. I couldn't find any titanium bits in town. But I stocked up on reverse drilling bits, carbide bits, titanium bits, and a drift punch.

My question is, what is directly behind the exhaust bolt if I was to drill clear thru, or use the drift punch to knock it thru? The picture below shows the area with the problem. It is the front bolt on the driver side. At the front of the head, just 'around the corner' from the broken stud, is what looks like a freeze plug, it has a small metal disc soldered to it that says "void if removed"
 

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Carbide bits are what I use to cut through broken high speed drill bits. They have two small chips of carbide brazed to the tip of the bit, and they are very hard, but brittle. Use slow speed, and they will cut long curly shavings through that bit like butter. Might try using a small nut to act as a drill bushing to keep it centered in the hole. Water passage on the other side of that stud. That's an overheat indicator on the freeze plug. Is there a warranty you are worried about? If not, pop that freeze plug out, and shove a grease covered rag in the hole to catch the shavings so they don't chew up your water pump seal.
 
First, thanks for all the tips and tricks from you guys I got in the last thread. I ended up getting the cobalt bit drilled out. It took lots of effort and about a dozen bits. But ultimately, I used the suggestion posted by a couple members, I ordered two solid carbide drill bits. The first bit did the trick.

My next concern is now that I've got it drilled out, I'm not sure how much torque I can put on the bolt extractor. I don't want to break it off in the bolt!

Does anyone have any ideas how much torque if can apply without the risk of breakage? Also, any additional tips from you guys that have had to do this before?
 

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bighammer said:
First, thanks for all the tips and tricks from you guys I got in the last thread. I ended up getting the cobalt bit drilled out. It took lots of effort and about a dozen bits. But ultimately, I used the suggestion posted by a couple members, I ordered two solid carbide drill bits. The first bit did the trick.

My next concern is now that I've got it drilled out, I'm not sure how much torque I can put on the bolt extractor. I don't want to break it off in the bolt!

Does anyone have any ideas how much torque if can apply without the risk of breakage? Also, any additional tips from you guys that have had to do this before?
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I switched to this type of extractor after snapping off a few of the style you are using. I have been very happy with them.
 

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I have a set of Snap On extractors like that, too short for what he's doing though, I think.
 
At this point I assume it's still not budging. I've broken off a few extractors before and feel your pain. Although I don't know the actual amount of torque you can use, my experiences have been easier if I had very little 'meat' left on the bolt I was extracting. From your picture it looks like the hole you drilled is off center. If it is, it'll be difficult to drill it out any larger without cutting into the threads in the head. - And your extractor may already be trying to grab the head on one side. You could always try a dremel tool to enlarge and re-center the hole if you need to.
 
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